libgccjit interrupt service routine error in psm v0.1.26 and stacker v0.1.21

This is an issue I discovered when building a stage 2 compiler.

PSM error:

libgccjit.so: error: : interrupt service routine can only have a pointer argument and an optional integer argument
libgccjit.so: error: : interrupt service routine must return ‘void’
error: failed to build archive at `/home/michal/rust/build/x86_64-unknown-linux-gnu/stage1-rustc/x86_64-unknown-linux-gnu/release/deps/libpsm-d68540d796768164.rlib`: failed to open object file: No such file or directory (os error 2)

stacker error:

libgccjit.so: error: : interrupt service routine should have a pointer as the first argument
error: failed to build archive at `/home/michal/rust/build/x86_64-unknown-linux-gnu/stage1-rustc/x86_64-unknown-linux-gnu/release/deps/libstacker-1003f9d5747170ec.rlib`: failed to open object file: No such file or directory (os error 2)

Question: what is an "interrupt service routine" in the context of GCC?

Start by reproducing the stage 2 compiler build described in the issue and compare the libgccjit diagnostics for psm v0.1.26 and stacker v0.1.21. Trace which generated functions trigger the interrupt-service-routine checks and determine whether the failure is in the codegen path or dependency interaction. Done means the reported psm and stacker build failures no longer occur.